This invention relates to apparatus for sampling a liquid over an extended period.
Many known sampling devices incorporate pumps and motors, the speed or the frequency of operation of the pump being controlled by auxiliary devices. Other known sampling devices incorporate a number of evacuated bottles into which, when a valve in the neck of each bottle is opened, a small quantity of the liquid is sucked. The valves are usually controlled by a timing device. Some sampling devices are operated by compressed air. The sampling device is located beneath the surface of the liquid and liquid enters a chamber within the device through a non-return valve. At intervals determined by an auxillary device, a pulse of compressed air purges the chamber and forces the liquid through a tube to a collecting bottle above the surface of the liquid. All these devices are of elaborate construction and require careful maintenance. They are usually bulky and cannot be left unattended at remote locations; for example on a river bank. The pump and compressed air types also require a power supply.
A need exists for a liquid sampling apparatus which is of particularly simple construction.